Recommended psi
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Lead Driver
Joined: Sep 2003
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From: Albuquerque
Recommended psi
Anybody know what the recommended psi (front and back) on my '76 F-150 4x4? My truck doesn't have a nice sticker on the inner door post like the new ones with all that cool info 
Not that it should matter, but I am currently running 32"x11.5"x15 BFG A/T's on each corner.
Thanks!
Not that it should matter, but I am currently running 32"x11.5"x15 BFG A/T's on each corner.
Thanks!
Senior User
Joined: Mar 2001
Posts: 379
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Actually, tire size does matter. A truck is supported by the volume of air in a tire, not the pressure. So, a larger tire needs less pressure to support the same weight since it has a larger volume.
As far as what pressure to run you can go two ways,
make a chalk line accross the tire tread and drive a few feet on the pavement. If the chalk line is worn off in the middle but not on the edges you have too much air in them. If it's worn off more on the edges you have too little.
Another way is to take the GVWR that should be listed on the truck somewhere (if it's not you'll have to guess) and mathmatically come up with the proper presure. example:
Lets say your truck weighs 4500lb unloaded (pretty close weight for a reg. cab long bed 70's Ford 1/2 ton 4x4). Lets say the weight distibution is 65/35 (again, unloaded) that means the front tires have to support 2925lb and the rears support 1575lb divide both of those numbers by two since you have two tire supporting the weight. That give you roughly 1463lb per front tire and 788lb per rear tire. On the sidewall of the tire it will say the max weight the tire can support at some max pressure. Take the max weight and divide it by the weight the tire has to support. This will give you some decimal number. Multiply this number by the max pressure and that will give you the exact pressure you need to support the weight. Remember, if your frequently haul heavy loads the rear pressure will have to be brought up to support the additional weight. Failure to do so could cause a tire to blow out.
As far as what pressure to run you can go two ways,
make a chalk line accross the tire tread and drive a few feet on the pavement. If the chalk line is worn off in the middle but not on the edges you have too much air in them. If it's worn off more on the edges you have too little.
Another way is to take the GVWR that should be listed on the truck somewhere (if it's not you'll have to guess) and mathmatically come up with the proper presure. example:
Lets say your truck weighs 4500lb unloaded (pretty close weight for a reg. cab long bed 70's Ford 1/2 ton 4x4). Lets say the weight distibution is 65/35 (again, unloaded) that means the front tires have to support 2925lb and the rears support 1575lb divide both of those numbers by two since you have two tire supporting the weight. That give you roughly 1463lb per front tire and 788lb per rear tire. On the sidewall of the tire it will say the max weight the tire can support at some max pressure. Take the max weight and divide it by the weight the tire has to support. This will give you some decimal number. Multiply this number by the max pressure and that will give you the exact pressure you need to support the weight. Remember, if your frequently haul heavy loads the rear pressure will have to be brought up to support the additional weight. Failure to do so could cause a tire to blow out.
